#include<iostream>
using namespace std;
class A
{
public:
	int _a;
};
class B : public A
{
public:
	int _b;
};
class C : public A
{
public:
	int _c;
};
class D :public B, public C
{
	int _d;
};
int main()
{
	D d;
	d.B::_a = 10;
	d.C::_a = 20;
	d._b = 1;
	d._c = 2;
	return 0;
}